Field of the Invention:
The invention relates to a method for controlling and/or regulating an electrical energy system.
In the operation of an electric energy system it must be ensured that in the event of a fault in individual resources of the electric energy system the stability of the energy system as a whole can be maintained.
An electrical energy system in the sense of the invention is to be understood as meaning any system that is used for generating, transmitting or consuming electric energy. An electric energy system can be, for example, a medium-voltage or a low-voltage power supply network or a generator arrangement for generating electrical energy.
Electrical energy systems are subject to an increasing demand due to the supply of electrical energy from renewable energy sources, growing energy consumption and frequently changing load situations over time due to energy trading. These problems are exacerbated by an inadequate level of expansion of electric energy systems.
This leads to recurring violations of the stationary as well as the dynamic stability. In order to avoid large-scale shutdowns and blackouts after faults, suitable measures for dealing with the respective fault must be implemented very quickly to secure the stability of the network.
In the context of so-called “day-ahead” power plant planning it is common to operate a static congestion management system to ensure the stationary (n−1) security for the following day.
This does not protect against unexpected scenarios, however.
If such unpredictable scenarios do occur, load shedding relays are used to limit the impact of faults or accident situations. These relays are dimensions based on analyses that can be obtained from so-called offline studies. Thus measures can be introduced in a standardized way to secure the stability of the network.
An example of the use of relays is the so-called 5-level load shedding plan of the European Network of Transmission System Operators for Electricity (entso-e), in which in the energy distribution network switching devices are permanently assigned to the respective load shedding level. If a fault is found in a section of the power supply network, then in accordance with the first level, load is shed by means of the assigned switching equipment, and the impact on the energy supply is observed. If a danger to the stability of the network persists, then according to the next level even more load will be shed, and so on. Decision criteria for triggering a load shedding only involve locally measured values of voltage and network frequency, which are monitored against predefined threshold values.
Such a staged load shedding plan is designed with fixed parameters and therefore is not tailored to the particular fault and the particular operating state, so that sometimes too much or too little load is shed. The load shedding can also be carried out in the wrong section of the electric energy system. In addition, the local load shedding can only take place at low frequencies, because it is necessary first of all to wait for the system response to the activation of generator reserves. For this reason, the local load shedding is often not sufficient to safeguard the network stability. Furthermore, the coordination in international composite networks consisting of several national energy distribution networks is not always guaranteed. Also such a load shedding plan is often not tailored to suit the current state of development of the electrical energy system. Also, no coordination or combination of different measures is possible.
The SIGUARD “Phasor Data Processor” (PDP) software from Siemens AG is also known, in which time-synchronized phasor measurements (phasor measurements for current and voltage) from a plurality of phasor measurement units (PMUs) can be very rapidly provided online, summarized and stored in a database.
In addition, from the product brochure “SIGUARD Solutions, Dynamic security assessment with SIGUARD DSA”, dated September 2013 and from document EP 2052451 B1 which relates to this product, a method is known in which, based on the current system status, the dynamic behavior of an electric energy system is determined by simulation. In this way, the backup reserves of an electrical energy system are continuously determined afresh, in order to detect the possible impact of operating states and faults at an early stage and to propose measures to a user to prevent blackouts.